Instance termination script is executed for every terminated (forced by administrative or system) workflow instances. This script may be useful for rollback any Instance Opening Script operations.
When any error occurred while executing script workflow termination is aborted and all operations rollbacked also.
In script you can use $Instance to get or set initiated instance properties, $Initiator variable specifies the who is initiated workflow instance but variable can be null for module type tasks. You can also refer to right panel to list available scripting objects.
Unlike task prework or postwork scripts $Xml variable attached to data model root element, not the pool element.